A hierarchical research by large-scale and ab initio electronic structure theories -- Si and Ge cleavage and stepped (111)-2x1 surfaces --

TL;DR

This paper combines large-scale and ab initio electronic structure theories to study stepped Si(111)-2x1 and Ge(111)-2x1 surfaces, confirming predicted structures and revealing stable step-edge configurations.

Contribution

It demonstrates the hierarchical approach's effectiveness in understanding surface structures, validating predictions with ab initio calculations, and extending insights to germanium surfaces.

Findings

Confirmed stepped structure and STM images for Si(111)-2x1

Identified two stable step-edge structures

Extended analysis to Ge(111)-2x1 surfaces

Abstract

The ab initio calculation with the density functional theory and plane-wave bases is carried out for stepped Si(111)-2x1 surfaces that were predicted in a cleavage simulation by the large-scale (order-N) electronic structure theory (T. Hoshi, Y. Iguchi and T. Fujiwara, Phys. Rev. B72 (2005) 075323). The present ab initio calculation confirms the predicted stepped structure and its bias-dependent STM image. Moreover, two (meta)stable step-edge structures are found and compared. The investigation is carried out also for Ge(111)-2x1 surfaces, so as to construct a common understanding among elements. The present study demonstrates the general importance of the hierarchical research between large-scale and ab initio electronic structure theories.